U.S. patent application number 14/248935 was filed with the patent office on 2014-11-06 for apparatus and methods for low temperature measurement in a wafer processing system.
This patent application is currently assigned to Applied Materials, Inc.. The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Joseph M. RANISH.
Application Number | 20140330422 14/248935 |
Document ID | / |
Family ID | 51841888 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140330422 |
Kind Code |
A1 |
RANISH; Joseph M. |
November 6, 2014 |
APPARATUS AND METHODS FOR LOW TEMPERATURE MEASUREMENT IN A WAFER
PROCESSING SYSTEM
Abstract
Implementations disclosed herein relate to methods and apparatus
for zoned temperature control during a film forming process. In one
implementation, a substrate processing apparatus is provided. The
substrate processing apparatus comprises a vacuum chamber, a
plurality of power supplies coupled with the plurality of thermal
laps and a controller that adjusts the power supplies based on
input from radiation sensors. The chamber includes a sidewall
defining a processing region. A plurality of thermal lamps is
positioned external to the processing region. A window is
positioned between the plurality of thermal lamps and the
processing region. A radiation source is disposed within the
sidewall and oriented to direct radiation toward an area proximate
a substrate support. A radiation sensor is disposed on the side of
the substrate support opposite the plurality of thermal lamps to
receive emitted radiation from the radiation source.
Inventors: |
RANISH; Joseph M.; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
51841888 |
Appl. No.: |
14/248935 |
Filed: |
April 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61818338 |
May 1, 2013 |
|
|
|
Current U.S.
Class: |
700/121 |
Current CPC
Class: |
H01L 21/67248 20130101;
G05D 23/27 20130101; H01L 21/67115 20130101 |
Class at
Publication: |
700/121 |
International
Class: |
G05D 23/19 20060101
G05D023/19 |
Claims
1. A substrate processing apparatus, comprising: a vacuum chamber
comprising: a sidewall defining a processing region; a plurality of
thermal lamps positioned external to the processing region; a
window positioned between the plurality of thermal lamps and the
processing region; a radiation source disposed within the sidewall
and oriented to direct radiation toward an area proximate a
substrate support; and a radiation sensor disposed on the side of
the substrate support opposite the plurality of thermal lamps to
receive emitted radiation from the radiation source; a plurality of
power supplies coupled with the plurality of thermal lamps; and a
controller that adjusts the power supplies based on input from the
radiation sensors.
2. The substrate processing apparatus of claim 1, further
comprising: a reflective member positioned to direct the radiation
from the radiation source disposed within the sidewall toward the
radiation sensor.
3. The substrate processing apparatus of claim 2, wherein the
reflective member is positioned adjacent the window.
4. The substrate processing apparatus of claim 2, wherein the
reflective member is embedded in the window.
5. The substrate processing apparatus of claim 3, wherein the
reflective member is sized to fit between adjacent thermal lamps of
the plurality of thermal lamps.
6. The substrate processing apparatus of claim 1, wherein the
radiation sensor disposed within the sidewall is positioned behind
a window.
7. The substrate processing apparatus of 2, wherein the reflective
member is positioned between two pieces of sealed quartz.
8. The substrate processing apparatus of claim 2, wherein the
reflective member is a back surface coated mirror with a protective
layer disposed thereon.
9. The substrate processing apparatus of claim 1, wherein the
window is quartz.
10. The substrate processing apparatus of claim 1, wherein the
window is positioned above the sidewall and the plurality of
thermal lamps are positioned above the window.
11. The substrate processing apparatus of claim 1, wherein the
window is positioned below the sidewall and the plurality of
thermal lamps are positioned below the window.
12. The substrate processing apparatus of claim 1, wherein the
window is a transparent dome.
13. A method of processing a substrate, comprising: heating a
substrate disposed on a substrate support in a chamber having a
window by transmitting radiation from a plurality of lamps through
the window; depositing a layer on the substrate by flowing a
precursor gas across the substrate; detecting a first temperature
at a first zone of the substrate using a first radiation sensor
disposed on a side of the substrate support opposite the plurality
of lamps; detecting a second temperature at a second zone of the
substrate using a second radiation sensor disposed on the side of
the substrate support opposite the plurality of lamps; adjusting
power to a first portion of the plurality of lamps based on the
first temperature; and adjusting power to a second portion of the
plurality of lamps based on the second temperature.
14. The method of claim 13, further comprising: removing the
substrate from the chamber; flowing a cleaning gas comprising
chlorine, bromine, or iodine, into the chamber; removing the
cleaning gas from the chamber; and disposing a second substrate in
the chamber for processing.
15. The method of claim 14, wherein a temperature of the chamber is
maintained or increased while flowing the cleaning gas into the
chamber.
16. The method of claim 15, wherein the first zone is located a
first radial distance from a center of the substrate, the second
zone is located a second radial distance from the center of the
substrate, and the first radial distance is different from the
second radial distance.
17. The method of claim 16, further comprising maintaining a
temperature gradient across the substrate.
18. A substrate processing apparatus, comprising: a vacuum chamber
comprising an upper transparent dome, a lower transparent dome, and
a sidewall positioned between the upper transparent dome and the
lower transparent dome; a plurality of thermal lamps positioned
proximate to either the upper transparent dome or the lower
transparent dome; a radiation source disposed within the sidewall
and oriented to direct radiation toward an area proximate a
substrate support; a radiation sensor disposed on the side of the
substrate support opposite the plurality of thermal lamps to
receive emitted radiation from the radiation source; a plurality of
power supplies coupled with the plurality of thermal lamps in
relation to the position of the radiation sensor; and a controller
that adjusts the plurality of power supplies based on input from
the radiation sensor.
19. The substrate processing apparatus of claim 18, further
comprising: a reflective member positioned to direct the emitted
radiation from the radiation source disposed within the sidewall
toward the plurality of radiation sensors.
20. The substrate processing apparatus of claim 19, wherein the
reflective member is positioned adjacent the lower transparent
dome.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 61/818,338, filed May 1, 2013 which is herein
incorporated by reference in its entirety.
FIELD
[0002] Methods and apparatus for semiconductor processing are
disclosed herein. More specifically, implementations disclosed
herein relate to methods and apparatus for zoned temperature
control during a film forming process.
BACKGROUND
[0003] Semiconductor processes such as epitaxy are used extensively
in semiconductor processing to form very thin material layers on
semiconductor substrates. These layers frequently define some of
the smallest features of a semiconductor device, and they may have
a high quality crystal structure if the electrical properties of
crystalline materials are desired. A deposition precursor is
normally provided to a process chamber in which a substrate is
disposed; the substrate is heated to a temperature that favors
growth of a material layer having desired properties.
[0004] It is generally desirable that the film have very uniform
thickness, composition, and structure. However, due to variations
in local substrate temperature, gas flows, and precursor
concentrations, it is quite challenging to form films having
uniform and repeatable properties. The process chamber is normally
a vessel capable of maintaining vacuum, typically below 10 Torr,
and heat is normally provided by heat lamps positioned outside the
vessel to avoid introducing contaminants. Control of substrate
temperature, and therefore of local layer formation conditions, is
complicated by thermal absorptions and emissions of chamber
components and exposure of sensors and chamber surfaces to film
forming conditions inside the process chamber. There remains a need
for a film-forming chamber with improved temperature control, and
methods of operating such a chamber to improve uniformity and
repeatability.
SUMMARY
[0005] Methods and apparatus for semiconductor processing are
disclosed herein. More specifically, implementations disclosed
herein relate to methods and apparatus for zoned temperature
control during a film forming process. In one implementation, a
substrate processing apparatus is provided. The substrate
processing apparatus comprises a vacuum chamber, a plurality of
power supplies coupled with the plurality of thermal laps and a
controller that adjusts the power supplies based on input from
radiation sensors. The chamber includes a sidewall defining a
processing region. A plurality of thermal lamps is positioned
external to the processing region. A window is positioned between
the plurality of thermal lamps and the processing region. A
radiation source is disposed within the sidewall and oriented to
direct radiation toward an area proximate a substrate support. A
radiation sensor is disposed on the side of the substrate support
opposite the plurality of thermal lamps to receive emitted
radiation from the radiation source. A reflective member may be
positioned to direct radiation from the radiation source disposed
within the sidewall toward the radiation sensor. The reflective
member may be positioned adjacent the window. The reflective member
may be embedded in the window. The reflective member may be sized
to fit between adjacent thermal lamps of the plurality of thermal
lamps. The radiation sensor disposed within the sidewall may be
positioned behind a window. The reflective member may be positioned
between two pieces of sealed quartz. The reflective member may be a
back surface coated mirror with a protective layer disposed
thereon. The window positioned between the plurality of thermal
lamps and the processing region may be quartz. The window may be
positioned above the sidewall and the plurality of thermal lamps
may be positioned above the window. The window may be positioned
below the sidewall and the plurality of thermal lamps may be
positioned below the window. The window may be a transparent
dome.
[0006] In another implementation, a method of processing a
substrate is provided. The method comprises heating a substrate
disposed on a substrate support in a chamber having a window by
transmitting radiation from a plurality of lamps through the
window. A layer is deposited on the substrate by flowing a
precursor gas across the substrate. A first temperature is detected
at a first zone of the substrate using a first radiation sensor
disposed on a side of the substrate support opposite the plurality
of lamps. A second temperature is detected at a second zone of the
substrate using a second radiation sensor disposed on the side of
the substrate support opposite the plurality of lamps. Power to a
first portion of the plurality of lamps is adjusted based on the
first temperature. Power to a second portion of the plurality of
lamps is adjusted based on the second temperature.
[0007] In yet another implementation, a substrate processing
apparatus is provided. The substrate processing apparatus comprises
a vacuum chamber comprising an upper transparent dome, a lower
transparent dome, and a sidewall positioned between the upper
transparent dome and the lower transparent dome. A plurality of
thermal lamps is positioned proximate to either the upper
transparent dome or the lower transparent dome. A radiation source
is disposed within the sidewall and oriented to direct radiation
toward an area proximate a substrate support. A radiation sensor is
disposed on the side of the substrate support opposite the
plurality of thermal lamps to receive emitted radiation from the
radiation source. A plurality of power supplies is coupled with the
plurality of thermal lamps in relation to the position of the
radiation sensor. A controller adjusts the plurality of power
supplies based on input from the radiation sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] So that the manner in which the above recited features of
the present disclosure can be understood in detail, a more
particular description of the disclosure, briefly summarized above,
may be had by reference to implementations, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical implementations
of this disclosure and are therefore not to be considered limiting
of its scope, for the disclosure may admit to other equally
effective implementations.
[0009] FIG. 1 is a schematic cross-sectional view of a process
chamber including a temperature control system according to some
implementations described herein;
[0010] FIG. 2 is a simplified isometric view of one implementation
of a rapid thermal process chamber (RTP) including another
temperature control system according to some implementations
described herein;
[0011] FIG. 3 is a schematic cross-sectional view of another
implementation of an RTP chamber including yet another temperature
control system according to some implementations described herein;
and
[0012] FIG. 4 is a flow diagram illustrating a method according to
some implementations described herein.
[0013] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one implementation may be beneficially used on other
implementations without specific recitation.
DETAILED DESCRIPTION
[0014] As used in this specification and the appended claims, the
singular forms "a" and "an" include plural referents unless the
context clearly indicates otherwise. Thus, for example, reference
to "a radiation source" includes a combination of two or more
radiation sources, and the like.
[0015] Methods and apparatus for semiconductor processing are
disclosed herein. More specifically, implementations disclosed
herein relate to methods and apparatus for zoned temperature
control in a film forming process. Current temperature measurement
systems position pyrometers within a heat source (e.g., a light
array) directed toward a substrate. In this position, the pyrometer
is affected by light from the light array, which affects the
precise measurement of the temperature of the substrate. Some
implementations described herein use a temperature control system
that performs transmission pyrometry. The temperature control
system may include a radiation source and a radiation sensor. The
radiation sensor is positioned away from the heat source to provide
a more accurate temperature measurement. The radiation sensor may
be adapted to measure radiation emitted from the radiation source
and through the substrate 108 as well as thermal radiation emitted
by the substrate. The radiation source may be positioned in a
sidewall of the process chamber. The radiation source may be
positioned to direct radiation through the substrate and to the
radiation sensor. A reflective member may be used to redirect the
radiation emitted by the radiation source from the sidewall of the
process chamber through the substrate and to the radiation sensor.
The radiation source may be a laser. The reflective member may be
semi-transparent so light from the light array is not
attenuated.
[0016] The temperature control system may include a transmitted
radiation detector system to measure radiation transmitted from a
radiation source through the substrate at first and second discrete
wavelengths and to compare intensity of the transmitted radiation
at the first discrete wavelength to the intensity of transmitted
radiation at the second discrete wavelength.
[0017] In some implementations the temperature dependence of the
bandgap energy of silicon is used to measure temperature. In some
implementations, the amount of energy transmitted through a silicon
substrate is measured, where the source for the measurement is also
the heating element in the chamber. In another implementation, two
measurements at two discrete wavelengths are obtained, and the
ratio of the measurements is compared. These implementations can
minimize variation in transmission unrelated to the bandgap
absorption (i.e., dopants, non-spectrally varying films), as well
as compensating for source variation. In another embodiment, two
discrete wavelength sources (LEDs or lasers) are fired
sequentially, and the measurements are compared (for example, by
time domain wavelength modulation). In some implementations,
rotating apertures may be used to modulate the radiation source
signal. These implementations are useful for measuring silicon
substrates or thin films in the presence of high background
radiation sources.
[0018] In some implementations described herein a transmission
pyrometer is used to measure temperatures of silicon wafers of less
than 500 degrees Celsius and even less than 250 degrees Celsius in
a rapid thermal processing chamber. Transmission pyrometers can
detect discrete wavelengths of radiation from a light source as it
is filtered by a silicon wafer. The absorption of the silicon in
some wavelength bands strongly depends upon the wafer temperature
and purity. The temperature measurement may be used for thermal
processing at no more than such temperatures or may be used to
control the pre-heating up to the point that a radiation pyrometer
can measure the wafer temperature, for example, at 400 to 500
degrees Celsius.
[0019] A low-temperature transmission pyrometer useful below about
350 degrees Celsius may be implemented with a silicon photodiode
with little or no filtering in the wavelength band between 1 and
1.2 .mu.m. A transmission pyrometer useful in a wavelength range
extending to 500 degrees Celsius includes an InGaAs diode
photodetector and a filter blocking radiation above about 1.2
.mu.m. Radiation and transmission pyrometers may be integrated into
a structure including an optical splitter receiving radiation from
a light pipe or other optical light guide and dividing the
radiation into respective beams directed at the transmission
pyrometer and the filter of the radiation pyrometer.
[0020] FIG. 1 is a schematic cross-sectional view of a process
chamber 100 including a temperature control system according to one
implementation described herein. The temperature control system
comprises a radiation source 140a, 140b (collectively 140), a
radiation sensor 170a, 170b (collectively 170), and optionally, a
reflective member 150a, 150b (collectively 150). The radiation
source 140 is disposed in a sidewall 110 defining a processing or
process gas region 156 of the process chamber 100 FIG. 1. The
radiation sensors 170 are positioned above a substrate support 107
whereas radiant heating lamps 102 are positioned below the
substrate support 107.
[0021] The process chamber 100 may be used to process one or more
substrates, including the deposition of a material on an upper
surface of a substrate 108. The process chamber 100 generally
includes an array of radiant heating lamps 102 for heating, among
other components, a back side 104 of a substrate support 107
disposed within the process chamber 100. The substrate support 107
may be a ring-like substrate support as shown, which supports the
substrate from the edge of the substrate, a disk-like or
platter-like substrate support, or a plurality of pins, for example
three pins. The substrate support 107 is located within the process
chamber 100 between an upper dome 128 and a lower dome 114. The
substrate 108 (not to scale) can be brought into the process
chamber 100 and positioned onto the substrate support 107 through a
loading port 103.
[0022] The substrate support 107 is shown in an elevated processing
position, but may be vertically traversed by an actuator (not
shown) to a loading position below the processing position to allow
lift pins 105 to contact the lower dome 114, passing through holes
in the substrate support 107, and raise the substrate 108 from the
substrate support 107. A robot (not shown) may then enter the
process chamber 100 to engage and remove the substrate 108
therefrom though the loading port 103. The substrate support 107
then may be actuated up to the processing position to place the
substrate 108, with its device side 116 facing up, on a front side
110 of the substrate support 107.
[0023] The substrate support 107, while located in the processing
position, divides the internal volume of the process chamber 100
into the processing or process gas region 156 (above the substrate)
and a purge gas region 158 (below the substrate support 107). The
substrate support 107 is rotated during processing by a central
shaft 132 to minimize the effect of thermal and process gas flow
spatial anomalies within the process chamber 100 and thus
facilitate uniform processing of the substrate 108. The substrate
support 107 is supported by the central shaft 132, which moves the
substrate 108 in an up and down direction 134 during loading and
unloading, and in some instances, processing of the substrate 108.
The substrate support 107 is typically formed from a material
having low thermal mass or low heat capacity, so that energy
absorbed and emitted by the substrate support 107 is minimized. The
substrate support 107 may be formed from silicon carbide or
graphite coated with silicon carbide to absorb radiant energy from
the lamps 102 and conduct the radiant energy to the substrate 108.
The substrate support 107 is shown in FIG. 1 as a ring with a
central opening to facilitate exposure of the substrate to the
thermal radiation from the lamps 102. The substrate support 107 may
also be a platter-like member with no central opening. In some
implementations, the substrate support 107 may have apertures or
windowed apertures for transmission of the radiation emitted by the
radiation source 140.
[0024] In general, the upper dome 128 and the lower dome 114 are
typically formed from an optically transparent material such as
quartz. The upper dome 128 and the lower dome 114 are thin to
minimize thermal memory, typically having a thickness between about
3 mm and about 10 mm, for example about 4 mm. The upper dome 128
may be thermally controlled by introducing a thermal control fluid,
such as a cooling gas, through an inlet portal 126 into a thermal
control space 136 and withdrawing the thermal control fluid through
an exit portal 130. In some implementations, a cooling fluid
circulating through the thermal control space 136 may reduce
deposition on an inner surface of the upper dome 128.
[0025] One or more lamps, such as an array of lamps 102, can be
disposed adjacent to and beneath the lower dome 114 in a specified,
optimal desired manner around the central shaft 132 to heat the
substrate 108 as the process gas passes over, thereby facilitating
the deposition of a material onto the upper surface of the
substrate 108. In various examples, the material deposited onto the
substrate 108 may be a group III, group IV, and/or group V
material, or may be a material including a group III, group IV,
and/or group V dopant. For example, the deposited material may
include gallium arsenide, gallium nitride, or aluminum gallium
nitride.
[0026] The lamps 102 may be adapted to heat the substrate 108 to a
temperature within a range of about 200 degrees Celsius to about
1,200 degrees Celsius, such as a temperature within a range of
about 300 degrees Celsius to about 950 degrees Celsius. The lamps
102 may include bulbs 141 surrounded by an optional reflector 143.
Each lamp 102 is coupled to a power distribution board (not shown)
through which power is supplied to each lamp 102. The lamps 102 are
positioned within a lamphead 145 which may be cooled during or
after processing by, for example, a cooling fluid introduced into
channels 149 located between the lamps 102. The lamphead 145
conductively cools the lower dome 114 due in part to the close
proximity of the lamphead 145 to the lower dome 114. The lamphead
145 may also cool the lamp walls and walls of the reflectors 143.
If desired, the lampheads 145 may or may not be in contact with the
lower dome 114.
[0027] A circular shield 167 may be optionally disposed around the
substrate support 107 and coupled to the sidewall 110 of the
chamber body 101. The shield 167 prevents or minimizes leakage of
heat/light noise from the lamps 102 to the device side 116 of the
substrate 108 in addition to providing a pre-heat zone for the
process gases. The shield 167 may be made from CVD SiC coated
sintered graphite, grown SiC, or a similar opaque material that is
resistant to chemical breakdown by process and cleaning gases.
[0028] A reflector 122 may be optionally placed outside the upper
dome 128 to reflect infrared light that is radiating off the
substrate 108 back onto the substrate 108. Due to the reflected
infrared light, the efficiency of the heating will be improved by
containing heat that could otherwise escape the process chamber
100. The reflector 122 can be made of a metal such as aluminum or
stainless steel. The process chamber 100 can have machined channels
to carry a flow of a fluid such as water for cooling the reflector
122. If desired, the efficiency of the reflection can be improved
by coating a reflector area with a highly reflective coating such
as with gold.
[0029] The temperature control system comprises radiation sources
140a, 140b, radiation sensors 170a, 170b, and optionally, the
reflective members 150a, 150b. The radiation sources 140a, 140b may
be optical sources. The radiation sensors 170a, 170b may be optical
sensors. Exemplary radiation sources include lasers, light emitting
diodes (LEDs), low power incandescent bulb or other suitable light
sources. The temperature control systems may comprise radiation
pyrometer systems and/or transmission pyrometer systems.
[0030] The radiation sources 140a, 140b are typically disposed at
different locations in the sidewall 110 to facilitate viewing
different locations of the substrate 108 during processing. The
radiation sources 140a, 140b may be positioned in apertures 142a,
142b formed in the sidewall 110. In some implementations, the
radiation sources 140a, 140b are exposed to the environment of the
process chamber 100. In some implementations where the radiation
sources 140a, 140b are exposed to the environment of the process
chamber 100, the radiation sources 140a, 140b may be coated with a
protective coating layer to protect the radiation sources 140a,
140b from processing chemistries used in the process chamber 100.
In some implementations, the radiation sources 140a, 140b are
isolated from the environment of the process chamber 100. The
radiation sources 140a, 140b may be isolated from the environment
of the process chamber 100 by windows 144a, 144b (collectively
144). The windows 144a, 144b are positioned over the apertures
142a, 142b. The windows 144a, 144b may be selected such that the
material of the windows 144a, 144b is transmissive to the radiation
emitted by the radiation sources 140a, 140b but reflective to the
radiation emitted by the radiant heating lamps. Exemplary materials
for the material of the windows 144a, 144b include quartz,
sapphire, tantalum, tantala (Ta.sub.2O.sub.5--SiO.sub.2), titania
(TiO.sub.2--SiO.sub.2), silica (SiO.sub.2), zinc, niobia and
combinations thereof. In some implementations, the windows 144a,
144b may be coated with a dielectric coating that is selective to
the wavelength of the radiation sources 140a, 140b.
[0031] In some implementations, the radiation sources 140a, 140b
may be provided with cooling to protect the radiation sources 140a,
140b from overheating. Cooling for the radiation sources 140a, 140b
may be provided by any suitable cooling sources or mechanisms.
Exemplary cooling sources and mechanisms include both active and
passing cooling sources (e.g., cooling fluids, chill plates or
housing, thermoelectric coolers (TEC or Peltier), and/or reflective
housings.
[0032] A plurality of radiation sensors 170a, 170b for measuring
radiation emitted from the radiation source 140a, 140b and through
the substrate 108 as well as thermal radiation emitted by the
substrate 108 are positioned on the side of the substrate support
107 opposite the radiant heating lamps 102. The sensors 170 are
typically disposed at different locations to facilitate viewing
different locations of the substrate 108 during processing. In some
implementations, the sensors 170 are disposed outside of the
process chamber 100, for example, above the upper dome 128. In some
implementations, the radiation sensors 170a, 170b are disposed
within the process chamber 100, for example, within the process gas
region 156. In some implementations, the sensors 170 may be
embedded within the upper dome 128.
[0033] Sensing transmitted radiation from different locations of
the substrate 108 facilitates comparing the thermal energy content,
for example the temperature, at different locations of the
substrate 108 to determine whether temperature anomalies or
non-uniformities are present. Such non-uniformities can result in
non-uniformities in film formation, such as thickness and
composition. The number of radiation sensors 170a, 170b typically
corresponds to the number of radiation sources 140a, 140b. At least
one sensor 170a, 170b is used, but more than one may be used.
Different implementations may use two, three, four, five, six,
seven, or more sensors 170.
[0034] Each sensor 170 views a zone of the substrate 108 and senses
the transmitted radiation to determine the thermal state of a zone
of the substrate. The zones may be oriented radially in some
implementations. For example, in implementations where the
substrate 108 is rotated, the sensors 170 may view, or define, a
central zone in a central portion of the substrate 108 having a
center substantially the same as the center of the substrate 108,
with one or more zones surrounding the central zone and concentric
therewith. It is not required that the zones be concentric and
radially oriented, however. In some implementations, zones may be
arranged at different locations of the substrate 108 in non-radial
fashion.
[0035] The sensors 170 may be attuned to the same wavelength or
spectrum, or to different wavelengths or spectra. For example,
substrates used in the chamber 100 may be compositionally
homogeneous, or they may have domains of different compositions.
Using sensors 170 attuned to different wavelengths may allow
monitoring of substrate domains having different composition and
different emission responses to thermal energy.
[0036] In certain implementations, the reflective members 150a,
150b are positioned in the process chamber 100 to direct radiation
from the radiation source 140a, 140b through the substrate 108 and
toward the radiation sensors 170. Each radiation sensor 170 may
have a corresponding reflective member 150. The number of
reflective members 150 in the process chamber 100 may be the same
as, less than, or greater than the number of thermal radiation
sensors 170. In certain implementations, each reflective member 150
may be positioned to reflect the greatest amount of emitted
radiation toward the reflective member's corresponding sensor
170.
[0037] The reflective members 150a, 150b comprise materials that
are reflective to the radiation emitted by the radiation sources
140a, 140b. The reflective members 150a, 150b may comprise
materials that are transparent to the radiation emitted by the
radiant heating lamps 102.
[0038] In certain implementations, the reflective members 150a,
150b are positioned on the same side of the substrate support 107
as the radiation sources 140a, 140b. The reflective members 150a,
150b may be positioned at the bottom of the process chamber 100.
The reflective members 150a, 150b may be positioned adjacent to the
lower dome 114. The reflective members 150a, 150b may be positioned
on the lower dome 114. The reflective members 150a, 150b may be
embedded in the lower dome 114. The reflective members 150a, 150b
may be disposed between the radiant heating lamps 102, for example
in the channels 149. In certain implementations, where the
reflective members 150a, 150b are transmissive to the radiant
energy emitted by the radiant heating lamps 102 but reflective to
the radiation emitted by the radiation sources 140a, 140b, the
reflective members 150a, 150b may be positioned over the lamphead
145.
[0039] In certain implementations, the reflective members 150a,
150b are encapsulated in quartz. The quartz may be sealed. In
certain implementations, the reflective members 150a, 150b are
mirrors with a back surface coated with a protective layer.
[0040] In some implementations where the reflective members 150a,
150b are exposed to the environment of the process chamber 100, the
reflective members 150a, 150b may be coated with a protective
coating layer to protect the reflective members 150a, 150b from
processing chemistries used in the process chamber 100.
[0041] In some implementations, the reflective members 150a, 150b
may be provided with cooling to protect the reflective members
150a, 150b from overheating. Cooling for the reflective members
150a, 150b may be provided by any suitable cooling sources or
mechanisms. Exemplary cooling sources and mechanisms include both
active and passing cooling sources (e.g., cooling fluids, chill
plates or housings, thermoelectric coolers (TEC or Peltier), and/or
reflective housings.
[0042] In certain implementations, the reflective members 150 are
oriented so as to provide the reflected beam substantially normal
to the substrate 108. In some implementations, the reflective
members 150 are oriented so as to provide the reflected beam normal
to the substrate 108, while in other implementations, the
reflective members 150 may be oriented so as to provide the
reflected beam in slight departure from normality. An orientation
angled within about 5.degree. of normal is most frequently
used.
[0043] A top thermal sensor 118 may be disposed in the reflector
122 to monitor a thermal state of the upper dome 128 and/or
substrate 108. Such monitoring may be useful to compare to data
received from the radiation sensors 170a, 170b, for example to
determine whether a fault exists in the data received from the
radiation sensors 170a, 170b. The top thermal sensor 118 may be an
assembly of sensors in some cases, featuring more than one
individual sensor. Thus, the chamber 100 may feature one or more
sensors disposed to receive radiation emitted from a first side of
a substrate and one or more sensors disposed to receive radiation
from a second side of the substrate opposite the first side.
[0044] A controller 160 receives data from the sensors 170 and
separately adjusts power delivered to each lamp 102, or individual
groups of lamps or lamp zones, based on the data. The controller
160 may include a power supply 162 that independently powers the
various lamps or lamp zones. The controller 160 can be configured
with a desired temperature profile, and based on comparing the data
received from the sensors 170; the controller 160 adjusts power to
lamps and/or lamp zones to conform the observed thermal data to the
desired temperature profile. The controller 160 may also adjust
power to the lamps and/or lamp zones to conform the thermal
treatment of one substrate to the thermal treatment of another
substrate, in the event some chamber characteristics drift over
time.
[0045] FIG. 2 is a simplified isometric view of one implementation
of a rapid thermal process chamber (RTP) 200 including another
temperature control system according to one implementation
described herein. Similar to the temperature control system
depicted in FIG. 1, the temperature control system of FIG. 2
comprises a radiation source 140, a radiation sensor 170, and
optionally a reflective member 150.
[0046] The process chamber 200 includes a substrate support 204, a
chamber body 202, having sidewalls 208, a bottom 210, and a top 212
defining an interior volume 220. A processing region 215 is defined
between the sidewalls 208, the substrate support 204 and the top
212. The sidewalls 208 typically include at least one substrate
access port 248 to facilitate entry and egress of a substrate 240
(a portion of which is shown in FIG. 2). The access port may be
coupled to a transfer chamber (not shown) or a load lock chamber
(not shown) and may be selectively sealed with a valve, such as a
slit valve (not shown).
[0047] In one implementation, the substrate support 204 is annular
and the chamber 200 includes a radiant heat source 206 disposed in
an inside diameter of the substrate support 204. The substrate
support 204 comprises an annular sidewall 252 with a substrate
support ring 254 disposed thereon for supporting substrate 240. The
radiant heat source 206 typically comprises a plurality of lamps.
Exemplary RTP chambers and methods of pyrometry that may be used
with the implementations described herein are described in U.S.
Pat. No. 7,112,763, U.S. Pat. No. 8,254,767, and United States
Patent Application Publication No. 2005/0191044.
[0048] In one implementation, the chamber 200 includes a plate 250
incorporating gas distribution outlets to distribute gas evenly
over a substrate to allow rapid and controlled heating and cooling
of the substrate. The plate 250 may be absorptive, reflective, or
have a combination of absorptive and reflective regions. In one
implementation, the plate 250 may have regions, some within view of
the radiation sensors 170, and some outside the view of the
pyrometers. The regions within view of the radiation sensors 170
may be about one inch in diameter, if circular, or other shape and
size as necessary. The regions within view of the radiation sensors
170 may be very highly reflective over the wavelength ranges
observed by the radiation sensors 170. Outside the wavelength range
and field of view of the radiation sensors 170, the plate 250 can
range from reflective to minimize radiative heat loss, to
absorptive to maximize radiative heat loss to allow for shorter
thermal exposure.
[0049] The radiation source 140 may be disposed in the sidewall 208
of the process chamber 200. In some implementations where multiple
radiation sources are used, the radiation sources 140 are typically
disposed at different locations in the sidewall 208 to facilitate
viewing different locations of a substrate 240 during processing.
The radiation source 140 may be positioned in an aperture 242
formed in the sidewall 208. In some implementations, the radiation
source 140 is exposed to the processing environment of the process
chamber 200. In some implementations where the radiation source 140
is exposed to the environment of the process chamber 200, the
radiation source 140 may be coated with a protective coating layer
to protect the radiation source 140 from processing chemistries
used in the process chamber 100. In some implementations, the
radiation source 140 is isolated from the environment of the
process chamber 100. The radiation source 140 may be isolated from
the environment of the process chamber 200 by a window 144 placed
over aperture 242. In some implementations, the radiation source
140 may be provided with cooling to protect the radiation source
140 from overheating as previously described herein.
[0050] The annular sidewall 252 of the substrate support 204 may
also have an aperture with a window 256 disposed therein for
allowing the beam from the radiation source 140 to reach the
reflective member 150. The window 256 may comprise any of the
materials described above for window 144.
[0051] In certain implementations, the reflective member 150 is
positioned in the process chamber 100 to direct radiation from the
radiation source 140 through the substrate 240 and toward the
radiation sensors 170. As described above, each radiation sensor
140 may have a corresponding reflective member 150. The number of
reflective members 150 in the process chamber 200 may be the same
as, less than, or greater than the number of radiation sensors 170.
In certain implementations, each reflective member 150 may be
positioned to reflect the greatest amount of emitted radiation
toward the reflective member's corresponding radiation sensor
170.
[0052] In certain implementations, the reflective member 150 is
positioned on the same side of the substrate support 204 as the
radiation source 140. The reflective member 150 may be positioned
at the bottom of the process chamber 200. The reflective member 150
may be positioned adjacent to the window 214. The reflective member
150 may be positioned on the window 214. The reflective member 150
may be embedded in the window 214. The reflective member 150 may be
disposed between the honeycomb tubes 260 of the radiant heat source
206. In certain implementations, the reflective member 150 may be
positioned over the honeycomb tubes 260 of the radiant heat source
206.
[0053] The RTP chamber 200 also includes a cooling block 280
adjacent to, coupled to, or formed in the top 212. Generally, the
cooling block 280 is spaced apart and opposing the radiant heat
source 206. The cooling block 280 comprises one or more coolant
channels 284 coupled to an inlet 281A and an outlet 281B. The
cooling block 280 may be made of a process resistant material, such
as stainless steel, aluminum, a polymer, or a ceramic material. The
coolant channels 284 may comprise a spiral pattern, a rectangular
pattern, a circular pattern, or combinations thereof and the
channels 284 may be formed integrally within the cooling block 280,
for example by casting the cooling block 280 and/or fabricating the
cooling block 280 from two or more pieces and joining the pieces.
Additionally or alternatively, the coolant channels 284 may be
drilled into the cooling block 280.
[0054] The inlet 281A and outlet 281B may be coupled to a coolant
source 282 by valves and suitable plumbing and the coolant source
282 is in communication with the controller 224 to facilitate
control of pressure and/or flow of a fluid disposed therein. The
fluid may be water, ethylene glycol, nitrogen (N.sub.2), helium
(He), or other fluid used as a heat-exchange medium.
[0055] In the implementation shown, the substrate support 204 is
optionally adapted to magnetically levitate and rotate within the
interior volume 220. The substrate support 204 shown is capable of
rotating while raising and lowering vertically during processing,
and may also be raised or lowered without rotation before, during,
or after processing. This magnetic levitation and/or magnetic
rotation prevents or minimizes particle generation due to the
absence or reduction of moving parts typically required to
raise/lower and/or rotate the substrate support.
[0056] The chamber 200 also includes a window 214 made from a
material transparent to heat and light of various wavelengths,
which may include light in the infra-red (IR) spectrum, through
which photons from the radiant heat source 206 may heat the
substrate 240. In one implementation, the window 214 is made of a
quartz material, although other materials that are transparent to
light maybe used, such as sapphire. In one implementation, the
window 214 is selected such that the material of the window 214 is
transmissive to the radiation emitted by the radiant heat source
206 but reflective to the radiation emitted by the radiation source
140. The window 214 may also include a plurality of lift pins 244
coupled to an upper surface of the window 214, which are adapted to
selectively contact and support the substrate 240, to facilitate
transfer of the substrate into and out of the chamber 200. Each of
the plurality of lift pins 244 are configured to minimize
absorption of energy from the radiant heat source 206 and may be
made from the same material used for the window 214, such as a
quartz material. The plurality of lift pins 244 may be positioned
and radially spaced from each other to facilitate passage of an end
effector coupled to a transfer robot (not shown). Alternatively,
the end effector and/or robot may be capable of horizontal and
vertical movement to facilitate transfer of the substrate 240.
[0057] In one implementation, the radiant heat source 206 includes
a lamp assembly formed from a housing which includes a plurality of
honeycomb tubes 260 in a coolant assembly (not shown) coupled to a
second coolant source 283. The second coolant source 283 may be one
or a combination of water, ethylene glycol, nitrogen (N.sub.2), and
helium (He). The housing walls 208, 210 may be made of a copper
material or other suitable material having suitable coolant
channels formed therein for flow of the coolant from the second
coolant source 283. The coolant cools the housing of the chamber
200 so that the housing is cooler than the substrate 240. Each tube
260 may contain a reflector and a high-intensity lamp assembly or
an IR emitter from which is formed a honeycomb like pipe
arrangement. This close-packed hexagonal arrangement of pipes
provides radiant energy sources with high power density and good
spatial resolution. In one implementation, the radiant heat source
206 provides sufficient radiant energy to thermally process the
substrate, for example, annealing a silicon layer disposed on the
substrate 240. The radiant heat source 206 may further comprise
annular zones, wherein the voltage supplied to the plurality of
tubes 260 by controller 224 may be varied to enhance the radial
distribution of energy from the tubes 260.
[0058] Dynamic control of the heating of the substrate 240 may be
affected by the one or more radiation sensors 170 adapted to
measure the temperature across the substrate 240.
[0059] In the implementation shown, an optional stator assembly 218
circumscribes the walls 208 of the chamber body 202 and is coupled
to one or more actuator assemblies 222 that control the elevation
of the stator assembly 218 along the exterior of the chamber body
202. In one implementation (not shown), the chamber 200 includes
three actuator assemblies 222 disposed radially about the chamber
body, for example, at about 120 degree angles about the chamber
body 202. The stator assembly 218 is magnetically coupled to the
substrate support 204 disposed within the interior volume 220 of
the chamber body 202. The substrate support 204 may comprise or
include a magnetic portion to function as a rotor, thus creating a
magnetic bearing assembly to lift and/or rotate the substrate
support 204. In one implementation, at least a portion of the
substrate support 204 is partially surrounded by a trough (not
shown) that is coupled to a fluid source 286, which may include
water, ethylene glycol, nitrogen (N.sub.2), helium (He), or
combinations thereof, adapted as a heat exchange medium for the
substrate support. The stator assembly 218 may also include a
housing 290 to enclose various parts and components of the stator
assembly 218. In one implementation, the stator assembly 218
includes a drive coil assembly 268 stacked on a suspension coil
assembly 270. The drive coil assembly 268 is adapted to rotate
and/or raise/lower the substrate support 204 while the suspension
coil assembly 270 may be adapted to passively center the substrate
support 204 within the process chamber 200. Alternatively, the
rotational and centering functions may be performed by a stator
having a single coil assembly.
[0060] An atmosphere control system 264 is also coupled to the
interior volume 220 of the chamber body 202. The atmosphere control
system 264 generally includes throttle valves and vacuum pumps for
controlling chamber pressure. The atmosphere control system 264 may
additionally include gas sources for providing process or other
gases to the interior volume 220. The atmosphere control system 264
may also be adapted to deliver process gases for thermal deposition
processes, thermal etch processes, and in-situ cleaning of chamber
components. The atmosphere control system 264 works in conjunction
with the showerhead gas delivery system.
[0061] The process chamber 200 also includes a controller 224,
which generally includes a central processing unit (CPU) 230,
support circuits 228 and memory 226. The CPU 230 may be one of any
form of computer processor that can be used in an industrial
setting for controlling various actions and sub-processors. The
memory 226, or computer-readable medium, may be one or more of
readily available memory such as random access memory (RAM), read
only memory (ROM), floppy disk, hard disk, or any other form of
digital storage, local or remote, and is typically coupled to the
CPU 230. The support circuits 228 are coupled to the CPU 230 for
supporting the controller 224 in a conventional manner. These
circuits include cache, power supplies, clock circuits,
input/output circuitry, subsystems, and the like.
[0062] In one implementation, each of the actuator assemblies 222
generally comprise a precision lead screw 232 coupled between two
flanges 234 extending from the walls 208 of the chamber body 202.
The lead screw 232 has a nut 258 that axially travels along the
lead screw 232 as the screw rotates. A coupling 236 is coupled
between the stator 218 and the nut 258 so that as the lead screw
232 is rotated, the coupling 236 is moved along the lead screw 232
to control the elevation of the stator 218 at the interface with
the coupling 236. Thus, as the lead screw 232 of one of the
actuators 222 is rotated to produce relative displacement between
the nuts 258 of the other actuators 222, the horizontal plane of
the stator 218 changes relative to a central axis of the chamber
body 202.
[0063] In one implementation, a motor 238, such as a stepper or
servo motor, is coupled to the lead screw 232 to provide
controllable rotation in response to a signal by the controller
224. Alternatively, other types of actuators 222 may be utilized to
control the linear position of the stator 218, such as pneumatic
cylinders, hydraulic cylinders, ball screws, solenoids, linear
actuators and cam followers, among others.
[0064] The process chamber 200 also includes one or more radiation
sensors 170, which may be adapted to sense radiation emitted from
the radiation source 140 and through the substrate 240 as well as
thermal radiation emitted by the substrate 240 before, during, and
after processing. In the implementation depicted in FIG. 2, the
radiation sensors 170 are disposed through the top 212, although
other locations within and around the chamber body 202 may be used.
The radiation sensors 170 may be adapted to couple to the top 212
in a configuration to sense the entire diameter of the substrate,
or a portion of the substrate. The radiation sensors 170 may
comprise a pattern defining a sensing area substantially equal to
the diameter of the substrate 240, or a sensing area substantially
equal to the radius of the substrate 240. For example, a plurality
of radiation sensors 170 may be coupled to the top 212 in a radial
or linear configuration to enable a sensing area across the radius
or diameter of the substrate 240. In one implementation (not
shown), a plurality of radiation sensors 170 may be disposed in a
line extending radially from about the center of the top 212 to a
peripheral portion of the top 212. In this manner, the radius of
the substrate 240 may be monitored by the radiation sensors 170,
which will enable sensing of the diameter of the substrate 240
during rotation.
[0065] As described herein, the chamber 200 is adapted to receive a
substrate in a "face-up" orientation, wherein the deposit receiving
side or face of the substrate is oriented toward the plate 250 and
the "backside" of the substrate is facing the radiant heat source
206. The "face-up" orientation may allow the energy from the
radiant heat source 206 to be absorbed more rapidly by the
substrate 240 as the backside of the substrate may be less
reflective than the face of the substrate.
[0066] The controller 224 receives data from the radiation sensors
170 and separately adjusts power delivered to each lamp of the
radiant heat source 206, or individual groups of lamps or lamp
zones, based on the data. The controller 224 may include a power
supply (not shown) that independently powers the various lamps or
lamp zones. The controller 224 can be configured with a desired
temperature profile, and based on comparing the data received from
the sensors 170; the controller 224 adjusts power to lamps and/or
lamp zones to conform the observed thermal data to the desired
temperature profile. The controller 224 may also adjust power to
the lamps and/or lamp zones to conform the thermal treatment of one
substrate to the thermal treatment of another substrate, in the
event some chamber characteristics drift over time.
[0067] The number of radiation sensors 170 typically corresponds to
the number of radiation sources 140. Although only one sensor is
depicted in FIG. 2, any number of sensors 170 may be used. For
example, different implementations may use two, three, four, five,
six, seven, or more sensors 170.
[0068] FIG. 3 is a schematic cross-sectional view of another
implementation of an RTP chamber 312 including yet another
temperature control system according to implementations described
herein. FIG. 3 schematically illustrates in cross section an RTP
reactor 310 described by Ranish et al. in U.S. Pat. No. 6,376,804
and is generally representative of the Radiance RTP reactor
available from Applied Materials, Inc. of Santa Clara, Calif. The
reactor 310 includes a process chamber 312, a substrate support 314
located within chamber 312, and a lamphead or radiant heat source
assembly 316 located on the top of the chamber 312, all generally
symmetrically arranged about a central axis 317.
[0069] Similar to the temperature control systems depicted in FIG.
1 and FIG. 2, the temperature control system of FIG. 3 comprises a
radiation source 140, a radiation sensor 170, and optionally a
reflective member 150.
[0070] The process chamber 312 includes a main body 318 having a
sidewall 319 and a window 320 resting on the sidewall 319 of the
main body 318. The main body and window define a processing region
321. The window 320 may be made of a material that is transparent
to infrared light, for example, clear fused silica quartz. In one
implantation, the window 320 is selected such that the material of
the window 320 is transmissive to the radiation emitted by the
radiant heat source assembly 316 but reflective to the radiation
emitted by the radiation source 140.
[0071] The main body 318 is made of stainless steel and may be
lined with quartz (not shown). A circular channel 322 is formed
near the bottom of the main body 318. The substrate support 314
includes a magnetic rotor 324 within the channel 322, a quartz
tubular riser 326 resting on or other coupled to the magnetic rotor
324, and a silicon-coated silicon carbide, opaque silicon carbide
or graphite edge ring 328 resting on the riser 326. During
processing, a substrate 330 or other substrate rests on the edge
ring 328. A magnetic stator 332 is located externally of the
magnetic rotor 324 and is magnetically coupled through the main
body 318 to induce rotation of the magnetic rotor 324 and hence of
the edge ring 328 and supported substrate 330 about the central
axis 317.
[0072] The window 320 rests on an upper edge of the main body 318
and an O-ring 334 located between the window 320 and the main body
318 provides an air-tight seal between them. The radiant heat
source assembly 316 overlies the window 320. Another O-ring 335
located between the window 320 and lamphead 316 provides an
airtight seal between them. The radiant heat source assembly 316
includes a plurality of lamps 336 that are supported by and
electrically powered through electrical sockets 338. The lamps 336
are preferably incandescent bulbs that emit strongly in the
infrared such as tungsten halogen bulb having a tungsten filament
inside a quartz bulb filled with a gas containing a halogen gas
such as bromine and diluted with an inert gas to clean the quartz
bulb. Each bulb is potted with a ceramic potting compound 337,
which is relatively porous. The lamps 336 are located inside
vertically oriented cylindrical lamp holes 339 formed on a
reflector body 340. More details of the reflector structure will be
provided later. The open ends of the lamp holes 339 of the
reflector body 340 are located adjacent to but separated from the
window 320.
[0073] The radiation source 140 may be disposed in the sidewall 319
of the process chamber 312. In some implementations where multiple
radiation sources are used, the radiation sources 140 are typically
disposed at different locations in the sidewall 319 to facilitate
viewing different locations of the substrate 330 during processing.
The radiation source 140 may be positioned in an aperture 382
formed in the sidewall 319. In some implementations, the radiation
source 140 is exposed to the environment of the process chamber
312. In some implementations where the radiation source 140 is
exposed to the environment of the process chamber 312, the
radiation source 140 may be coated with a protective coating layer
to protect the radiation source 140 from processing chemistries
used in the process chamber 312. In some implementations, the
radiation source 140 is isolated from the environment of the
process chamber 312. The radiation source 140 may be isolated from
the environment of the process chamber 312 by a window 144
positioned over the aperture 382. In some implementations, the
radiation source 140 may be provided with cooling to protect the
radiation source 140 from overheating as previously described
herein.
[0074] In certain implementations, the reflective member 150 is
positioned in the process chamber 312 to direct radiation from the
radiation source 140 through the substrate 330 and toward the
radiation sensor 170. Each radiation sensor 140 may have a
corresponding reflective member 150. The number of reflective
members 150 in the process chamber 100 may be the same as, less
than, or greater than the number of radiation sensors 170. In
certain implementations, each reflective member 150 may be
positioned to reflect the greatest amount of radiation toward the
reflective member's corresponding radiation sensor 170.
[0075] In certain implementations, the reflective member 150 is
positioned on the same side of the substrate support 314 as the
radiation sources 140. The reflective member 150 may be positioned
at the top of the process chamber 312. The reflective member 150
may be positioned on the window 320. The reflective member 150 may
be positioned adjacent to the window 320. The reflective member 150
may be embedded in the window 320. The reflective members 150 may
be disposed between the lamp holes 339 of the radiant heat source
assembly 316. In certain implementations, the reflective member 150
may be positioned over the lamp holes 339 of the radiant heat
source assembly 316.
[0076] A cooling chamber 342 is defined within the reflector body
340 by upper and lower chamber walls 344, 346 and a cylindrical
wall 348 and surrounds each of the lamp holes 339. A coolant, such
as water, introduced into the chamber via an inlet 350 and removed
at an outlet 352 cools the reflector body 340 and traveling
adjacent the lamp holes 339 cools the lamps 336. Baffles 354 may be
included to ensure proper flow of the coolant through the chamber.
Clamps 356 secure and seal the window 320, the radiant heat source
assembly 316, and the main chamber body 318 to one another.
[0077] The radiation sensor 170 may be optically coupled to and
disposed adjacent respective apertures 358 in a reflector plate 359
and supported in the main body 318 to detect a temperature or other
thermal property of a different radial portion of the lower surface
of the substrate 330. The radiation sensor 170 is connected to a
power supply controller 360, which controls the power supplied to
the infrared lamps 336 in response to the measured temperatures.
The infrared lamps 336 may be controlled in radially arranged
zones, for example, fifteen zones, to provide a more tailored
radial thermal profile to account for thermal edge effects. The
radiation sensor 170 provides signals indicative of a temperature
profile across the substrate 330 to the power supply controller
360, which controls the power supplied to each of the zones of the
infrared lamps 336 in response to a measured temperature. In some
implementations, the reactor 310 comprises seven or more radiation
sensors 170.
[0078] The main body 318 of the process chamber 312 includes a
processing gas inlet port 362 and a gas outlet port 364. In
operation, the pressure within the process chamber 312 can be
reduced to a sub-atmospheric pressure prior to introducing a
process gas through the inlet port 362. The process chamber is
evacuated by pumping through a port 366 by means of a vacuum pump
367 and a valve 363. The pressure is typically reduced to between
about 1 and 160 torr. Certain processes, however, can be run at
atmospheric pressure, though often in the presence of a specified
gas and the process chamber does not need to be evacuated for such
processes.
[0079] Another vacuum pump 368 reduces the pressure within the
lamphead 316, particularly when the process chamber 312 is pumped
to a reduced pressure to reduce the pressure differential across
the window 320. The pressure within the lamphead 316 is reduced by
pumping though a port 369 including a valve 365, which extends
through the cooling chamber 342 and is in fluid communication with
an interior space of the reflector body.
[0080] A pressurized source 375 of a thermally conductive gas, such
as helium, fills the radiant heat source assembly 316 with the
thermally conductive gas to facilitate thermal transfer between the
lamps 336 and the cooling channels 342. The pressurized source 375
is connected to the radiant heat source assembly 316 through a port
376 and a valve 377. The thermally conductive gas is introduced
into a space 378 formed between a lamphead cover 380 and the base
of each lamp 336. Opening the valve 377 causes the gas to flow into
this space 378. Since the lamp potting compound 337 is porous, the
thermally conductive gas flows through the potting compound 337 and
around the walls of each lamp 336 to cool it.
[0081] The controller 360 receives data from the radiation sensors
170 and separately adjusts power delivered to each lamp 336 of the
radiant heat source assembly 316, or individual groups of lamps or
lamp zones, based on the data. The controller 360 may include a
power supply (not shown) that independently powers the various
lamps or lamp zones. The controller 360 can be configured with a
desired temperature profile, and based on comparing the data
received from the sensors 170; the controller 360 adjusts power to
lamps and/or lamp zones to conform the observed thermal data to the
desired temperature profile. The controller 360 may also adjust
power to the lamps and/or lamp zones to conform the thermal
treatment of one substrate to the thermal treatment of another
substrate, in the event some chamber characteristics drift over
time.
[0082] FIG. 4 is a flow diagram illustrating a method according to
implementations described herein. FIG. 4 is a flow diagram
summarizing a method 400 according to another implementation. At
block 402, a substrate is positioned on a substrate support in a
process chamber. Exemplary process chambers are described in FIG.
1, FIG. 2 and FIG. 3. The substrate support is substantially
transparent to thermal radiation and has low thermal mass. Thermal
lamps are positioned to provide heat to the substrate. The thermal
lamps may be positioned either above the substrate support or below
the substrate support.
[0083] At block 404, a process gas is introduced to the process
chamber. The pressure of the process chamber may be set between
about 0.01 Torr and about 10 Torr. The process gas may be any gas
from which a layer is to be formed on the substrate. The process
gas may contain a group IV precursor and/or group III and group V
precursors, from which a group IV material, such as silicon or
germanium, or a group III/V compound material, such as aluminum
nitride, may be formed. Mixtures of such precursors may also be
used. The process gas may be flowed with an unreactive diluent or
carrier gas, and may be provided in laminar or quasi-laminar flow
substantially parallel to the substrate surface.
[0084] At block 406, the substrate may be heated to a temperature
between about 400.degree. C. and about 1,200.degree. C., for
example about 600.degree. C. The substrate may be heated by heating
source (e.g., a plurality of lamps as described above). The
precursors contact the heated substrate surface and form a layer on
the substrate surface. The substrate may be rotated to improve
uniformity of film properties.
[0085] At block 408, a first temperature of a first zone of the
substrate is measured by a first radiation sensor and a second
temperature of a second zone of the substrate is measured by a
second radiation sensor. The radiation sensors are used in
conjunction with the radiation sources and optional reflective
members described herein. In some implementations, the signals
received from the radiation sensors may be adjusted to compensate
for background radiation emanating from the lamps and reflected
from the substrate. The substrate optical properties as a function
of temperature, along with the known intensity of light emitted by
the lamps, may be used to model the intensity of reflected light,
and the modeled intensity used to adjust the signals from the
radiation sensors to improve the signal to noise ratio of the
sensors. In some implementations, another technique to compensate
for extraneous radiation received by the radiation sensor is to
chop or pulse the radiation source 140 at a frequency different
from the heating sources and use filtering electronics (e.g., a
lock-in amplifier and/or software) to separate the pulsed signal
from the background radiation.
[0086] At block 410, power to the heat source is adjusted based on
the first temperature and the second temperature readings to
conform the first temperature to a first target temperature and to
conform the second temperature to a second target temperature. The
first and second target temperatures may be the same or different.
For example, to compensate for faster film formation at an edge of
the substrate than at the center of the substrate, the first
temperature may be measured at the center of the substrate, the
second temperature may be measured at the edge of the substrate,
and lamp power adjusted to provide a higher substrate temperature
at the center than at the edge of the substrate. More than two
zones may be used to monitor temperatures at more than two
locations on the substrate to increase the specificity of local
temperature control, if desired.
[0087] At block 412, processing is stopped and the substrate is
removed from the process chamber. At block 414, a cleaning gas is
provided to the chamber to remove deposits from chamber surfaces.
Removing the deposits corrects reduction in transmissivity of
chamber components to lamp radiation and to substrate emissions,
maintaining repeatability of film properties from substrate to
substrate. The cleaning gas is typically a gas containing chlorine,
bromine, or iodine. Gases such as Cl.sub.2, Br.sub.2, I.sub.2, HCl,
HBr, and HI are often used. When elemental halogens are used,
temperature of the chamber may be held approximately constant, or
increased slightly, to clean the chamber. When hydrogen halides are
used, temperature of the chamber is typically increased to
compensate for reduced concentration of halogen cleaning agents.
Temperature of the chamber during cleaning with hydrogen halides
may be increased to between about 800.degree. C. and about
1,200.degree. C., for example about 900.degree. C. After cleaning
from 30 seconds to 10 minutes, depending on the desired cleaning
result, another substrate may be processed.
[0088] While the foregoing is directed to implementations of the
present disclosure, other and further implementations of the
disclosure may be devised without departing from the basic scope
thereof, and the scope thereof is determined by the claims that
follow.
* * * * *